Implement request's redirect mode and RequestRedirect for Fetch

Source/modules/fetch/Request.idl

Index: Source/modules/fetch/Request.idl
diff --git a/Source/modules/fetch/Request.idl b/Source/modules/fetch/Request.idl
index d658461882b2044186c356197683934cfb405e20..0fef4acc7f1f8fba4db643d02b1e21dba4713191 100644
--- a/Source/modules/fetch/Request.idl
+++ b/Source/modules/fetch/Request.idl
@@ -15,6 +15,7 @@ enum RequestContext {
 };
 enum RequestMode { "same-origin", "no-cors", "cors" };
 enum RequestCredentials { "omit", "same-origin", "include" };
+enum RequestRedirect { "follow", "error", "manual" };
 
 [
     Constructor(RequestInfo input, optional Dictionary requestInitDict),
@@ -32,6 +33,7 @@ enum RequestCredentials { "omit", "same-origin", "include" };
     readonly attribute DOMString referrer;
     readonly attribute RequestMode mode;
     readonly attribute RequestCredentials credentials;
+    readonly attribute RequestRedirect redirect;
 
     [RaisesException] Request clone();
 };